It is therefore the object of the present invention to propose a lightweight, easy-to-handle reflector screen with a wider field of application.
This object is achieved by a reflector screen of the kind mentioned hereinbefore by the fact that the reflective element is composed of at least two reflective sections, the two reflective sections each having a different geometrical shape in a section containing the axis of rotation of the reflector screen. The “section containing the axis of rotation” means a section parallel to the centre axis or axis of rotation, as shown in the figures. This means that the covering described or formed by the reflective element in section describes a curve which is composed of different geometrical curve sections. Due to this embodiment according to the invention, it is possible with a single reflector screen to combine or mix the reflective properties of several geometrical bodies.
An appropriate embodiment of the invention provides that the two reflective sections are located one behind the other in relation to the axis of rotation or centre axis of the reflector screen. This guarantees diverse adjustment of the light and shadow effects with easy handling.
Advantageously, one reflective section in the opened-up state of the reflector screen corresponds to an ellipse in section, and the other reflective section corresponds to a parabola in section, in which case it goes without saying that the geometrical bodies or curve sections are also encompassed in approximate form. By this means the essential reflections or light ray paths can be obtained, so that additional reflector screens etc. can be dispensed with.
A preferred development of the invention is distinguished in that, in addition to the supporting and tensioning structure, there is provided a further tensioning means which is designed and arranged in such a way that one of the reflective sections can be subjected to an additional tensioning force. By means of the supporting and tensioning structure, which usually has individual spokes, the shape of an ellipse or a nearly elliptical shape can be presented. However, to produce a parabola, considerable greater bending of the spokes is necessary, which is not economical with the traditional materials. Due to the additional tensioning means, shaping the reflective element into a parabola is particularly appropriate and cheap.
Preferably, between the parabolic reflective section and the spokes of the supporting and tensioning structure are arranged tensioning elements. By allocation of the tensioning elements to the spokes and the associated distribution of tensioning elements round the circumference of the body of revolution, particularly precise shaping of the reflective section is ensured. To put it another way, in spite of the great curvature of the parabolic reflective section, uniform tensioning without creases is ensured.
A particularly appropriate embodiment of the invention is characterised in that the tensioning elements are each composed of fabric elements that can be stretched essentially perpendicularly to the reflective element. In addition to a very lightweight and therefore particularly easy-to-handle design of the tensioning elements, uniform application of the tensioning force over a long distance is guaranteed as well.